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Single & double stack full disk comparison 20 September 2022

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#1 Averton

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Posted 20 September 2022 - 07:06 AM

It was forecast that there would be a bit more time before the clouds rolled in today, but not enough to consider setting up for an animation. Also it was quite windy and the seeing was only average. So we decided to take a image with our usual double stack arrangement using the Daystar Solar Scout 60 and the Lunt 40 etalon and compare this with the Lunt 40 single stacked. It shows that the Lunt 40 is a pretty good instrument in its own right.

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  • 2022-09-20 full disk small.jpg
  • 2022-09-20 full disk SS small.jpg

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#2 Averton

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Posted 20 September 2022 - 07:06 AM

Inverted images.

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  • 2022-09-20 full disk inv small.jpg
  • 2022-09-20 full disk SS inv small.jpg

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#3 phobos2

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Posted 20 September 2022 - 01:59 PM

Nice images!  Newbie here: what is a "DS60"? I googled it and didn't find anything.


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#4 BYoesle

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Posted 20 September 2022 - 03:43 PM

"we decided to take a image with our usual double stack [DS] arrangement using the Daystar Solar Scout 60 and the Lunt 40 etalon..." Emphasis added.


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#5 peterm

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Posted 20 September 2022 - 09:53 PM

DS =  Definitely Superior!  Super images Clare & Peter.


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#6 R Botero

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Posted 21 September 2022 - 02:18 AM

Great comparison! :waytogo:

Roberto
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#7 Averton

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Posted 21 September 2022 - 03:27 AM

Great comparison! waytogo.gif

Roberto

Thanks Roberto :)



#8 Averton

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Posted 21 September 2022 - 03:31 AM

DS =  Definitely Superior!  Super images Clare & Peter.

Thanks Peter :)

It was interesting to re-visit the Lunt 40 as when we first were using it we did not take flats or have the tilt adapter.  We have also changed much of our processing so we wanted to see how the images came out using our current methods.

While the double stack is better we think the Lunt 40 still does a pretty presentable job.



#9 Averton

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Posted 21 September 2022 - 03:48 AM

Nice images!  Newbie here: what is a "DS60"? I googled it and didn't find anything.

Thanks.

The DS60 is indeed a Daystar Solar Scout 60.  The 60 stands for 60mm aperture however this is not the aperture that is being used in these images.

The story goes that our first Ha scope was a Lunt 40 which at the time of purchase was being advertised as having a double stack option being available "soon".  After discussions with Lunt it turned out that there is no time frame for a double stack option so we went looking for an alternative. 

The Daystar Solar Scout 60 is a single stack scope also without any provision for double stacking.  We have also found that its stand alone single stack images aren't particularly good.  We knew this at the time of purchase and did not intend to use it single stacked.  We feel that it's performance issues are tied to the optics of the scope rather than the internal etalon.  The scope is advertised as F15.5 and a focal length of 930mm.  It has an internal barlow of 4.2 magnification which also has an added element so that the exiting beam is telecentric.  This means that the objective of the actual scope is figured for a focal ratio of F3.69.  This is a pretty wild bit of glass, you don't see too many refractors at this speed.  True it only has to focus a single narrow wavelength but it makes for a difficult lens.  In Daystar's own documentation for their stand alone Quarks they recommend operating them at F25 minimum and F30 preferred. 

So what does this mean for the Solar Scout is that a number of people have got better results by using an aperture mask to bring the focal ratio to F25 or greater. This means a mask of 40mm or less.  After all if you are using the centre bit of a lens, there's going to be less issues.

Knowing this our intention was always to use the 40mm front mounted air-space etalon from the Lunt 40 on the front of the Solar Scout to a) make it double stacked and b) reduce it's aperture to hopefully improve it's performance.  By and large, we feel that this has been successful. 

The idea then was just to compare our current double stacked images taken this way with images taken with the stock single stacked Lunt.  Both set ups have an aperture of 40mm determined by the Lunt etalon so they are direct comparisons.  We didn't include a single stacked image from the Solar Scout, either as standard with a 60mm aperture or with an aperture mask of 40mm, as neither of those images would have come close to the Lunt 40.

Hope this makes sense and explains the images.


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#10 phobos2

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Posted 21 September 2022 - 06:36 AM

"we decided to take a image with our usual double stack [DS] arrangement using the Daystar Solar Scout 60 and the Lunt 40 etalon..." Emphasis added.

Ouch... should have figured that out.  blush.gifblush.gifblush.gifblush.gif



#11 ETXer

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Posted 21 September 2022 - 08:01 PM

Very nice!

 

I've been dabbling with H-alpha imaging with my Questar, but also thinking about a dedicated solar scope, specifically to obtain full-disk images without too much added hassle. I had been considering a used PST, but it looks like the Lunt 40 is something to think about. And the ASI 178MM seems to match well also.

 

Cheers, Allan


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#12 Averton

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Posted 22 September 2022 - 08:18 AM

Very nice!

 

I've been dabbling with H-alpha imaging with my Questar, but also thinking about a dedicated solar scope, specifically to obtain full-disk images without too much added hassle. I had been considering a used PST, but it looks like the Lunt 40 is something to think about. And the ASI 178MM seems to match well also.

 

Cheers, Allan

Hi Allan,

We have never owned or used a PST but from what other people have said and posted, the Lunt 40 is definitely an improvement.  What we can say, is from our experience the Lunt 40 provides excellent results with a minimum of fuss. As you have observed, the ASI178MM does match it quite well.  The other option is the popular solar camera ASI174MM but you do need to use a barlow to bring the disk up to size.  The only complication with this is that you need about 1.5x magnification which can be achieved by taking the lens element off a standard x2 barlow and screwing it directly to the camera nose piece, but unfortunately this nose piece is still just slightly too long and needs to be shortened.  If you search the forum using the advanced search for Lunt 40 and ASI174 you will find a post from someone with details of their set up to make it work. 

The ASI178MM does have an issue with solar work where a grid pattern can sometimes be seen in the background.  Flat frames do help with this.


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#13 ETXer

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Posted 22 September 2022 - 08:36 PM

Hi Allan,

We have never owned or used a PST but from what other people have said and posted, the Lunt 40 is definitely an improvement.  What we can say, is from our experience the Lunt 40 provides excellent results with a minimum of fuss. As you have observed, the ASI178MM does match it quite well.  The other option is the popular solar camera ASI174MM but you do need to use a barlow to bring the disk up to size.  The only complication with this is that you need about 1.5x magnification which can be achieved by taking the lens element off a standard x2 barlow and screwing it directly to the camera nose piece, but unfortunately this nose piece is still just slightly too long and needs to be shortened.  If you search the forum using the advanced search for Lunt 40 and ASI174 you will find a post from someone with details of their set up to make it work. 

The ASI178MM does have an issue with solar work where a grid pattern can sometimes be seen in the background.  Flat frames do help with this.

Excellent, thanks for the info! I do have an ASI174MM (that I use with the Questar, Quark Combo, and a 2.5x Powermate). I have to say I like the simplicity of a Lunt 40/PST with a 178MM plus a low-profile focus adapter.


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#14 StarHugger2

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Posted 23 September 2022 - 12:48 PM

Nice comparison, Some nice images coming from the Lunt 40mm all around...
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#15 Averton

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Posted 24 September 2022 - 03:51 AM

Nice comparison, Some nice images coming from the Lunt 40mm all around...

Thanks Aaron :)




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